I like to chain compressors for vocals but if I had to choose one I would probably go the FET.
The FET is probably more of a all rounder because it has more tweakable parameters.
I think I prefer the FET over the RE2A, hard to decide though.
I would suggest trying the D.CAM ChanComp first before the FET or RE2A because of it's price. It's a very nice compressor and I tend to prefer it over the FET and RE2A on Kicks and Snares but not all the time. I also like it on Vocals.
I think having a range of compressors from different developers does make a difference in how your mix sounds.